1. Field of the Invention
The present invention relates to high intensity lighting fixtures, and in particular, to unjacketed, double-ended high intensity discharge (HID) lamps and fixtures for wide area lighting of relatively distant targets, such as in sports lighting.
2. Problems in the Art
High intensity discharge lamps, such as used in sports lighting, require high operating electrical power to operate lamps that usually are on the order of 1000 watts or greater. Also, HID lamps such as metal halide or mercury HID lamps generate ultraviolet (UV) radiation. Both of these characteristics of such HID lamps create safety issues, particularly for persons that install, maintain or repair such fixtures.
Some HID fixtures address these issues by utilizing screw-in lamps so that there are no directly exposed current-carrying parts. These lamps also usually have glass envelopes surrounding the arc tube. The glass absorbs a sufficient amount of UV radiation so that it does not pose a serious risk to workers, even if in close proximity to the lamps when operating.
A particular type of HID lamp does not have any glass envelope surrounding the arc tube. It also has opposite ends usually with short leads with exposed ends that are connected to exposed electrical connection posts in the fixture. Although such fixtures usually have glass lens over the front of the reflector for the fixture, which blocks UV radiation, when the lens is opened, that UV protection is removed. Also, the exposed current carrying surfaces pose risk.
Entities such as Underwriters Laboratories (UL) have standards for such fixtures (also sometimes called luminaries), which directly address the safety concerns with high-powered electricity and UV radiation relative to double-ended unjacketed HID lamps. See, for example, UL standards 1598. Sections 3.4, 6.4, and 6.5 require each fixture to have safety interlock switches which automatically disconnect electrical power to the fixture when the lens assembly is removed. The automatic disconnection of power is not only intended to prevent any risk of electrical shock, even if normally current carrying exposed surfaces are touched, but also, is intended to prevent any risk of UV exposure.
The state of the art follows these standards by either jacketing HID lamps or utilizing some type of automatic power disconnect, usually by some type of switch or switches. Some embed electrically conducting wire or ribbon in the lens. If the lens is broken, the wire or ribbon is broken and causes an automatic disconnect of power to the fixture, or at least to the exposed current-carrying parts or surfaces.
The problems with these types of state of the art solutions include the risk of failure of the automatic switches. The environment of these switches, in fixtures operating at high power and putting out significant heat, can result in unreliability for the automatic power disconnect switches or other automatic power disconnect structure(s).
Also, such switch(es) and structure(s) add to the complexity and cost of such fixtures. They can also add to the difficulty in accessing, working on, and replacing or repairing parts in the fixture.
Many types of the state of the art fixtures require use of tools to install and remove the lamps or other parts. Many times these fixtures are elevated to substantial heights in the air (e.g. on poles 35 feet to over 100 feet tall) or in rafters or on other elevated structures. It is cumbersome and adds additional risk to the worker to have to handle tools as well as be careful about not dropping anything, avoiding electrical shock and avoiding burns.
Therefore, there is a real need in the art for improvement. It is therefore a principle object, feature, or advantage of the present invention to improve upon the state of the art.